The work is directed at elucidating structure-function relationships in human and canine serum lipoproteins and at defining the physico-chemical basis of the interactions of these lipoproteins with cells. Low- and high density lipoproteins will be studied by a combination of physical methods (small-angle x-ray scattering, electron microscopy, analytical ultracentrifuge and differential scanning colorimetry) to be complemented by detailed structural investigation of the apolipoproteins (solubility studies, graded denaturation and lipid binding) and of selected fragments thereof obtained by chemical synthesis. Enzymatic probes, both proteolytic and lipolytic, will be used to probe the polar surface of native and re-assembled lipoproteins. For the study of lipid protein interactions, blood granulocytes and cultured skin fibroblasts will be used.